Note: Island Universe Cosmology is not, nor does it aspire to be, a cosmological model. Instead it is a kind of survey of the empirical evidence, as presented in our direct cosmological observations, that are then strung together with some standard physics. It will never achieve a unified picture of physical reality is not a unitary entity. It will always be a open-ended compendium of overlapping Island Universes.

1. Basic physics

2. Two fundamental states

• Matter – 3-Dimensional, localized objects with rest mass.
• Energy – 4-Dimensional, non-local, electromagnetic radiation – massless, transverse expanding spherical waves. Electromagnetic radiation (EMR) is the fundamental form of energy. Expanding spherical waves (ESW) are the cosmological-scale form of EMR.
• ESWs are standard physics.
• Everywhere there is no matter in the Cosmos, there is energy in the form of EMR.
• ACER, the Ambient Cosmic Electromagnetic Radiation flowing throughout the Cosmos
• Matter emits and absorbs energy (EMR).
• Space and time are relational concepts not substantive, causally interacting entities.

3. Extent of the Cosmos is unknown and assumed unknowable.

• The observable Cosmos is limited to the distance implied by the cosmological redshift.
• The night sky is bright at 2.7K (CMB) – resolves Olbers’ paradox.
• The CMB is the redshifted light from the most distant galaxies – those that completely cover the dome of the sky, blocking any radiation from more distant galaxies.

4. On cosmological scales (radius > 100 million lightyears)

• EMR should be modeled as successive Expanding Spherical Wavefronts
• ESWs are emitted by galaxies
• Gradually absorbed by outlying galaxies and other matter.
• Redshift is caused by the gradual absorption (energy loss) of an ESW by intervening matter.
• A cosmological redshift can be calculated by applying standard gravitational redshift math to an ESW at successive cosmological distances

5. The speed of light in the Cosmos is not a constant.

• As stipulated by Einstein and observed (Shapiro delay), the speed of light varies with position in a gravitational field, slowing as the field strengthens.
• Since E/m=c² it follows directly that as the speed of light declines, a material body undergoing gravitational collapse should shed mass by releasing energy (EMR).
• Consequently any gravitational collapse will be self-limiting and should produce a compact, luminous, highly gravitating body with an intrinsic gravitational redshift.
• Quasars fit that description.
• There is a considerable body of observational evidence that quasars are not at their redshift-implied distances.

6. Gravity, Matter, and Electromagnetic Radiation

• All gravitational effects arise from the interaction of matter and energy.
• Energy density gradients around massive bodies track gravitational effects.
• The cosmological redshift is caused by an energy-matter interaction (Section 4.)

7. A proper geometric framework for the Cosmos uses polar coordinates. 

• Appropriate for modeling expanding spherical wavefronts.
• Appropriate for modeling the local point-of-view of the Cosmos from any 3D location because any 3D local observer is at the center of their unique observable Cosmos.
• The POV frame does not have physical significance i.e. the shell implied by a given radial distance is not a physical shell or epoch. The shell or epoch only exists with respect to the observer; other observers in different cosmological settings will see different shells/epochs, similar in structure but different in content.

Earlier version: Island Universe Cosmology v3.2